1. Field of the Invention
This invention relates to an apparatus for and method of dispensing a powder-like material by gravity flow with substantial uniformity and minimum contamination of the immediate environment.
2. Prior Art Statement
There are numerous applications in industry where it is necessary to dispense a powder-like material or powder on a workpiece to enable further processing of such workpiece. Particularly in the art of making fibrous blankets or webs comprised of a workpiece defined as a controlled thickness layer of disconnected randomly disposed fibers or fiber lengths which are to be bonded together by an adhesive material, such as a resin provided in powder form, it is especially important to dispense the resin with as much uniformity of resin distribution as possible and with minimum contamination of the immediate vicinity or environment. Fibrous blankets or webs of the character mentioned, once made, are often used in making carpet underlays and mats used for thermal and accoustical insulation in various applications, including motor vehicles such as automobiles, and the like.
Numerous apparatus and methods have been proposed previously for dispensing or strewing resin on workpieces consisting of layers of disconnected randomly disposed fibers. However, these previously proposed apparatus and methods do not provide uniform distribution of the resin on such workpiece and/or provide excessive contamination of the environment, particularly the immediate environment, thereby producing a health and safety hazard.
For example, one proposed apparatus utilizes a fluted roll which is rotated beneath a bottom discharge opening of a hopper filled with resin. A brush roll is rotated against the fluted roll to help remove resin particles which generally lodge in the flutes.
Another type of resin strewer utilizes a resin container which has a bottom opening which discharges resin on an inclined vibratory plate disposed beneath such opening. The plate is vibrated by a suitable vibrating mechanism and the amplitude and frequency of the plate vibration is controlled in an effort to control the flow of resin from such plate.
Still another type of resin strewer uses a cylindrical pipe provided with spaced discharge holes in the lower portion thereof. Resin is moved along the pipe by a conventional feed screw and such screw forces resin through the discharge holes with rotation of the feed screw.
An enclosed material conveying system is also known where a material such as a powder or the like, is moved through an enclosed pipe system arranged in an endless loop utilizing an endless chain which is moved within the pipe system and such chain has chain flights fastened thereto at spaced intervals for dragging the material therealong. A typical system of this type is manufactured and sold by Hapman Division/ PRAB Conveyers, Inc., 6002 East Kilgore Rd., Kalamazoo, Mich. 49003.